+=== 5^SET/LOCAL_NODE^Add node to the local_node group
+=== 5^UNSET/LOCAL_NODE^Remove node from the local_node group
+The 'local_node' group is a group of nodes that you want a user
+to perceive as effectively one big node. At the moment, this extends
+only to announcing whenever a user is logging in or out of one of
+the nodes in the group (if those users have SET/LOGININFO).
+
+The local node group is as setup on this node. If you want the other
+nodes to also include this node and all the other nodes specified, then
+you must get those nodes to also run this command (or rcmd them to do
+so).
+
+In principle, therefore, each node determines its own local node group
+and these can overlap with other nodes' views.
+